Creation of a Small Animal Imaging Resource Program (SAIRP) at the University of Pennsylvania supporting research by investigators at this institution and also at the Fox Chase Cancer Center and Thomas Jefferson University is proposed. This SAIRP will provide three imaging modalities -- 1) Magnetic Resonance Imaging and Spectroscopy (MRI/S). 2) optical imaging covering the ultraviolet through near infrared (UV-NIR), and positron emission tomography (PET). The MRI/S facilities are now in place; the UV-NIR and PET facilities are now operational on the scale of human patients and will be adapted to studies of small animals (mice and rats) by the end of the first year. The SAIRP will support the research of 13 NIH funded projects dealing with 1) modification of tumor response to radiation and hyperthermia, 2) methods of monitoring tumor hypoxia, 3) gene therapy of brain tumors, 4) immunotherapy of tumors, 5) detection of breast cancer and 6) detection of tumor response to chemotherapy and radiation therapy. Ancillary facilities for redox scanning, NIR time resolved spectroscopoy, electronics, animal management, synthesis of contrast agent and physiological probes, histology, computer resources, biostatistics and MR of perfused cells will be provided. Research and development and D) projects will be directed towards the development of novel NMR capabilities that will enhance the research capabilities of the base projects. These R and D projects are: A. MRI of Small Animal Tumors, including: A1. Small Animal Microimaging. A2. Functional Imaging of Tumors, B. Multinuclear Spectroscopy, including: B1. Chemical Shift Selective MR Imaging of 31P in Animal Tumors, B2. 1H{17O} MRI of Tumors, B3. In Vivo Imaging of Intra- and Extracellular Na+ and pH in Tumors, and C. NMR Techniques for Monitoring Gene Therapy of Brain Tumors.